There has been a need for timer valves which permit flow of water for certain periods of time. These valves include a water inlet and an outlet. A water source, such as a spigot, is connected to the inlet while a hose or other watering device is coupled to the outlet. The valve is controlled by a timing device which will open the valve and keep it open to allow water flow to the outlet. In such a manner, a user simply sets the timer for a determined period of time. The user does not have to return to the valve to shut off the water flow to prevent over watering.
Various timer mechanisms have been used in the past. For example an electric timer has been used. Electronic timers may be analog or digital and may also use electrical power to actuate the valve. Such timers are very accurate, but suffer from several shortcomings. If the electrical power is supplied by a battery, the timer has a limited life. Further, the timer must be constructed to protect the battery from outside elements increasing the weight of the device and the number of component parts. Alternatively, electrical power may be supplied through a standard electrical outlet. However, this limits the effective range of the valve as it must be placed in proximity to an electrical outlet in order to function. Also, electrical devices have some safety risk due to electrical shock.
Another type of timer which has been used is a water driven timer such as that described in U.S. Pat. No. 4,708,264. Such a timer has an impeller interposed between the inlet and outlet of the valve and is rotated by the water flow. A gearing system is coupled to the impeller to eventually activate the valve to stop the water flow. The impeller based timer is self running and thus does not require an independent power source. However, this type of timer suffers from inaccuracy as the rotational speed of the impeller depends entirely on water flow which may not be constant from source to source. In addition, if the water flow is low pressure, the valve may not shut off properly.
A variety of valves have used mechanical wind up timers. These timers do not require an external power source and operate using a spring which is wound up and gradually released to activate the valve. However, such timers are mechanically complex and require more internal space in the valve housing thus increasing manufacturing costs. Further, since the timing mechanism does not directly couple to the valve, additional torque must be generated by the spring and thus the valve is not as efficient.
Thus, there is a need for a mechanical timer in which the mechanical components are in-line with the valve to conserve space. There is a further need for a mechanical timer which is accurate but requires no outside power sources. There is also a need for a mechanical timer which has a less complex assembly.